Initial evidence from the Nutritional Prevention of Cancer (NPC) trial suggests that selenium supplementation reduces the risk of prostate cancer among men with normal baseline PSA (prostate specific antigen) levels, and low selenium blood levels. However, in this study, selenium did not reduce the risk of lung, colorectal, or basal cell carcinoma of the skin. It actually increased the risk of squamous cell skin carcinoma. The ongoing Selenium and Vitamin E Cancer Prevention Trial (SELECT) aims to definitively address the role of selenium in prostate cancer prevention.
Uses of Selenium With Some Scientific Evidence
- Antioxidant -- Selenium is a key component of glutathione peroxidase, which has antioxidant properties in humans.
- Prevention of Prostate Cancer -- Men with normal PSA (prostate specific antigen) levels and low selenium levels may be able to reduce their risk of prostate cancer through selenium supplementation. It is not clear if selenium supplementation is beneficial for men diagnosed with prostate cancer or for men with normal or high selenium levels.
Uses of Selenium With Unclear or Contradictory Evidence
- Asthma -- There are some reports that selenium may help asthma symptoms. More research is needed.
Cancer Treatment -- People with cancer are more likely to have low selenium levels, but no one knows why. There's ongoing research to determine the effect of selenium on both cancer prevention and cancer treatment. Right now, there is nothing clear.
Cardiovascular Disease Prevention -- Theoretically, the antioxidant properties of selenium should help in the prevention of heart disease and other cardiovascular conditions. The research, however, has been mixed.
Chemotherapy -- There are mixed results about whether or not selenium is helpful to people undergoing chemotherapy for cancer. One concern is that the antioxidant properties of selenium might actually work to protect the cancer cells from the effects of chemotherapy. Selenium should not be taken by people undergoing chemotherapy without discussing it with an oncologist first.
Quality of Life for the Elderly -- Some reports indicate that selenium supplementation improves the mood and quality of life for elderly persons.
Potential Risks of Too Much Selenium
Some of the potential risks of consuming too much selenium include:- hair loss
- nail loss
- nausea
- skin disorders
- neurologic disorders
Selenium in Foods
The following list shows some of the foods that have selenium:- brewer’s yeast
- wheat germ
- butter
- garlic
- grains
- sunflower seeds
- walnuts
- raisins
- liver
- kidneys
- shellfish
- fish
Sources: National Library of Medicine – Drug and Supplement Information. Selenium.
